1. Field of the Invention
The present invention relates to a pneumatic tire, more particularly to a run-flat tire having an improved tire profile capable of improving run-flat performance of the tire without sacrificing running performance under normal conditions.
2. Description of Related Art
Recently, there is a strong demand for run-flat tires capable of running safely for a certain distance at a usual speed, for example, at a speed of 80 km/h for at least 80 km distance.
Hitherto, widely employed as a means of providing ability to run under flat conditions is to dispose a reinforcing rubber layer in each sidewall portion of a conventional type pneumatic tire. Such tires are disclosed in the laid-open Japanese patent applications JP-A-53-18104, JP-A-64-30809, JP-A-4-154411 for examples.
In such tires, however, it is difficult to satisfy the above-mentioned requirements, at least 80 km distance at 80 km/h, because the sidewall reinforcing layer is inevitably increased in the thickness, volume and weight. And when such a great mass of sidewall reinforcing rubber layer is disposed, tire performance under normally inflated conditions is liable to deteriorate. For example, the tire weight and rolling resistance increase, and fuel consumption of vehicles is increased, and further the ride comfort is not good, and furthermore belt edge loose is liable to occur to decrease the durability.